1. Field of the Invention
The present invention relates to a disk cartridge in which a recording disk medium is rotatably enclosed within a housing made up of upper and lower metal shells, and more particularly to the assembled structure of the housing.
2. Description of the Related Art
In mobile equipment such as digital cameras, etc., a very small disk cartridge, called “clik!™” such as that described in U.S. Pat. No. 6,256,168, is in use as a recording medium. This disk cartridge 1 is 50 mm in width, 55 mm in depth, and 1.95 mm in thickness, as schematically shown in FIG. 12. It has a housing, which is constructed of a resin frame 2, and upper and lower metal shells 3, 4 formed from a stainless steel sheet of 0.2 mm in thickness. Within the housing, there is rotatably enclosed a magnetic disk of diameter 1.8 inch (about 45.7 mm) which has a recording capacity of 40 MB. The housing is equipped with a U-shaped opening 6 through which a magnetic head is positioned over a recording surface of the magnetic disk, and a rotary shutter 7 that covers the U-shaped opening 6 when read and write operations are not performed. As illustrated in FIG. 12, the upper and lower shells 3, 4 are laser welded at 10 or more positions P with the upper and lower circumferential wall portions abutting each other.
The assembled structure of the housing in the above-described conventional disk cartridge, however, has the following problems: (1) an expensive, special machine such as a laser welding machine is required and the upper and lower shells need to be precisely positioned so they are not shifted from each other; (2) paper or sputter dust particles occur at the time of welding, adhere to a recording medium, and have an adverse influence on read and write operations, and also contaminate assembly space (which requires a class 100 to 1000 clean room); (3) in the case of welding the circumferential edges of upper and lower shells, at welded portions the circumferential edge of one shell is provided with tabs protruding slightly from the other shell, and consequently, at portions other than the welded portions there occur slight gaps between both circumferential edges and the problem of the occurrence of dust particles will arise; and (4) when disassembling the welded upper and lower shells for recycling or collection of classified refuse, the welded portions have to be destroyed and therefore the operation of disassembling them is time-consuming.